The ad showing a real-life female doctor breaks new ground in the women`s underwear business. Sure, former Baltimore Orioles star Jim Palmer boosted Jockey sales, aroused female fans and spun off a hunk poster when he posed in Jockey briefs, but a woman doctor?

Pirie, a Phoenix osteopath, says she posed for the Jockey for Her ad not so much for the money, but because she believes in the cotton product ``for gynecologic reasons.``

While some of Pirie`s medical colleagues find the Jockey ad unbefitting a professional woman, the doctor is a pro at showing off her physique. A sports medicine expert and exercise physiologist, Pirie works out to keep her body in the same peak form as when she copped the Miss U.S.A. title from the International Federation of Body Builders in 1982.

Her book, ``Getting Built,`` contains a slew of pictures of Pirie in more advanced states of undress than seen in the ad. The cover shows her in a competition pose. Rippling musculature is revealed to the extent a bikini allows.

``I believe in 100 percent cotton undies for gynecologic purposes,``

Pirie said. She and John Schmeizer, her husband and business manager, own the North Phoenix Health Institute.

Pirie, who is the institute`s medical director and also on the staffs of three area hospitals, said: ``It`s a quality product and I don`t think I need to lower myself to represent anything less than the best.

``I didn`t jump at the chance to be a model. A physician is more prestigious than a model.

``I certainly made sure the ad would be professional and tasteful and I am confident it is. As far as lingerie and underwear are concerned, there is no reason I should be shy.``

That aside, another female physician and sports medicine expert, Dr. Mona Shangold, director of sports gynecology at Georgetown University Hospital, Washington, D.C., said she wouldn`t pose in underpants, considering such a thing, for herself, unprofessional conduct.

``I don`t like what it conveys,`` Shangold said.

Asked what it does convey, Shangold replied, ``Sex object.``

But Pirie doesn`t see it that way. ``I`m a physician and I`m trained to handle subjects that are intimate in a mature way,`` she said.

``I looked at this product and saw how it was going to be presented and then I endorsed it. Standing in front of a sink in underpants as you change is not sexy or erotic.``

Shangold also disagrees with Pirie`s echo of the popular notion that cotton underpants are better than panties made of other fabrics on grounds that cotton ``breathes,`` helping to prevent vaginitis.

That fact really is not pinned down or accepted by the gynecologic community as gospel, according to Shangold, who is an assistant professor at Georgetown University Medical School.

Shangold and her pediatrician husband, Dr. Gabe Mirkin, medical editor of Runners World magazine, say in their book, ``The Complete Sports Medicine Book for Women,`` that there is no proof that underpants of synthetic fabrics trigger or contribute to vaginitis.

Mirkin, whose physique could compare favorably with Palmer`s on the male perfection scale, was asked if he would ever consider posing in an underwear ad.

``Indeed not,`` he said.

At the American College of Surgeons headquarters in Chicago, a spokesman said the group does not comment on such matters as a physician and surgeon posing in an ad in underpants. Pirie is not a member of the College, the spokesman said.

The American College of Obstetricians and Gynecologists in Washington, D.C., also refused to comment.

But in Phoenix, Pirie`s husband says he`s happy with feedback from the ad, ``a deal that took seven months to put together.``

He said Pirie has been teased good-naturedly by area doctors. In a letter, Dr. Lee Stein, president of the American Osteopathy Association, based in Chicago, congratulated and lightly teased Pirie for her precedent-breaking venture as an undies ad model.

``You`re our only Mead-Johnson research recipient (to study shoulder disorders) to appear in national magazines,`` he wrote Pirie.

Schmeizer says Pirie was well-paid for the ad but would not disclose the figure.